RV Holding Tanks vs Composting Toilet

The motorhome/RV “sewage” topic – particularly composting toilets vs holding tanks – seems to garner a lot of interest. It has been beaten to death and it is one of those topics that elicits a lot of passionate opinions. It is almost dangerous to respond to the topic on an Internet forum. I figured I’d note my thoughts on the subject and then never have to discuss it again!! 🙂

Nonetheless; this date is a particularly fine one to talk about icky, nasty things.

I consider a “typical” motorhome setup to consist of two holding tanks – a black (sewage) and grey (water from the sinks/shower). A 3″ valve on each tank and a large 3″ hose that connects the tank valve to the pipe into which the tanks are being dumped. Usually the two valves feed into a common pipe/fitting for the hose.

The process for dumping the tanks is to connect your hose to the pipe in the ground and to the connector on the motorhome. Then open the valves. Typically, the black tank valve is opened first and that tank drained. The grey tank valve is opened next. This is to use the “less gross” water to rinse out the “more gross” water. The draining is accomplished using gravity to do the work. Nearly all dump sites that I’ve used have a non-potable rinse hose available to squirt a bit of water thru the sewage hose after disconnecting it from the motorhome (but still connected to the pipe in the ground). You then disconnect the hose from the ground, re-install the caps at each end, and stow it.

My implementation of this on Missy is a wee bit different because I installed a single holding tank – both black and grey in a single tank. The process for dumping is the same, except I only open one valve.

Note that the liquid on the ground in the photo above is fresh water from a leaking faucet. It is NOT spilled icky stuff.

I know there are variations of this.

A macerator pump. This chews up the bits from the holding tank and pumps it all thru a smaller diameter hose. This must work ok as people sell these but I’ve heard a number of horror stories – I have no experience with them though. The legitimate use that I have heard is when the contents of the tank must go uphill. This requires the macerator pump since gravity can’t do the job. Regardless of the reason, this is adding a number of failure points/modes to an operation that one does not want to fail. The idea of taking fairly large chunks of “solids” (poo and toilet paper), ripping it all into small bits, and pumping it thru a small diameter hose just seems to be fraught with problems. I would avoid this approach to the greatest extent possible.

Some folks empty their tanks into a “tote” – a “mobile tank”. They haul this tank to a dump site and empty it. I understand that this is done to avoid having to move ones trailer/RV. It seems like a horrible idea to me – handling sewage more than has to be done seems like a recipe for problems. But again, I have no experience.  I can imagine that having to hookup a trailer – and remove the manual jacks that often accompany them – could be a real nuisance.

There are probably many others variations that I have not heard about.

It seems that some/many of the people that have had a bad “dumping” experience like to portray the “holding tank” concept as a horrible, horrible thing. They stink, you get gross sewage splattered all over yourself, they stink, parts fail, they stink, people put the wrong things down the toilet, they stink, valves leak, they stink, etc…

Notice, the stink part – this is a point of emphasis for some.

First and foremost, you will likely smell a holding tank system that is not properly vented. A plumbing system with a failed air admittance valve will likely stink. A toilet that does not properly hold a bit of water might stink. Sticking your nose inside your sewage hose and taking a big whiff – will likely stink. Those are all plumbing system problems. Well, the last one is probably a psychological problem. 🙂

A properly constructed and maintained holding tank and plumbing system will NOT stink. Sure, stick your face into the holding tank itself and you will be greeted with a smell that you might not like but you should never smell this inside the motorhome/RV. If you do smell your tank/plumbing system, something is not right.

There are some amusing stories that people use to “hate” on holding tanks and/or the dumping process. Their child tossed a big toy down the toilet and it plugged something up . You might consider what that same action would do to a house sewage system – that ain’t pretty either. A macerator pump that failed half-way thru a dump. A macerator line (small diameter hose) got plugged. Yep – all ugly situations – don’t blame the holding tanks though – blame the macerator pump and/or small diameter hose. Oh yes, the poo pyramid! This is caused by not properly using your system. Usually by leaving the black tank valve open when connected to a full hook up site (sewer hookup). All the liquids quickly drain down the hose while the solids collect it a big pyramid inside the tank. Sorry – not the tanks fault, this is operator error.

Toilet paper is another hot topic. Some people believe that you can only use that toilet paper that is microscopically thin and that everybody (??) hates. That is incorrect. Any toilet paper that is septic system approved will work. There is a simple test. Put a piece of toilet paper in a jar, fill it with water, and shake for a few seconds. Does the paper start to disintegrate? If so, it is acceptable to use.

Sometimes one might hear that dump sites are difficult to find and/or few and far between. I’ve only been in a limited areas (basically the Mississippi to the Pacific coast) so cannot speak to the ENTIRE nation, continent, or world. Where I have traveled, more than enough dump sites exist. I suppose if one had two days of capacity, it could be a problem. I have plenty of capacity so I am never in a situation where I MUST find a dump site TODAY. In fact, I usually dump well before my tanks are anywhere near full. The RVDumpSites.net and SaniDumps.com websites are both useful resources. Most RV parks have a dump site, some rest stops have them, some state visitor centers have them, most state park campgrounds have them, and of course, many truck stops and gas stations have them.

Finally, this approach does use some of your water supply. However; an RV toilet does not use anywhere near as much as a residential toilet.  I don’t know how to measure it but I would guess my use is less than one quart per flush.  When the entire bottom of the toilet bowel opens up – everything simply falls into the holding tank. A quick squirt of water with the hand sprayer rinses the remainder out.

In my opinion, RV holding tanks and their use is NOT a negative thing/experience – assuming proper installation, maintenance, and operation.  The reason I am posting this is NOT to convince anyone that one way is better than the other – there are far too many factors for that. Rather, it is to make sure the inexperienced have a balanced view of the options.

Onto composting toilets which are often touted as the easiest and best option available – in all circumstances. I’m sure they are in some circumstances. Perhaps one such circumstance is a very small rig with very small holding tanks or maybe a converted vehicle in which there is VERY limited space for holding tanks. However; I suspect some folks are ignoring at least some of the realities of a composting toilet in an RV/Motorhome.

Please do not confuse the topic with a composting toilet in a boat – that is an entirely different thing. There are many additional reasons to have one in a boat and dumping the contents is an entirely different matter.

There is no doubt that having compost for growing things is a neat deal – if you are growing things – particularly outside. Most people living in an RV/motorhome are not growing things outside.  Some focus on this “solids” aspect and seem to ignore the disposal of the liquids AND/OR the paper that is used (some say the paper does not go in the compost, others say it does – I don’t know). To REALLY make compost (to either toss in the garbage or use in the soil) takes a good bit of time. It appears to depend on several factors but, in general, it means carrying that stuff around for at least three months.  I would assume this means RV’ers are emptying their composting toilet into a composting bucket, stiring it every few weeks, and then throwing it out several months later once it has fully “cooked” (composted).  If a composting toilet takes a month to “fill” then it would seem a person would need at least three of these composting buckets??  Seems like that could take up a good bit of space.

For those folks that are just dumping the liquids outside, I suspect you have either not looked into the legality of such a thing or you don’t care. From listening to the NON-answers about how people deal with this – I suspect most composting toilet users do not care and are just dumping this stuff wherever they happen to be. Good or bad for the environment? Good or bad for the next camper that parks in your spot? Legal or illegal??  If you are considering a composting toilet, you might want to look into this.

A short discussion with a Forest Service or BLM ranger will yield an answer. It’s also pretty easy to find an answer to legality question of putting poo in a bag and dropping it in the garbage. Judging by the number of people that are willing to break the law while driving a vehicle, I assume they are also willing to break most other laws as well. Finally, a composting toilet needs proper venting – just like a holding tank.

I am NOT against composting toilets.

I think they are a great deal. For me and my motorhomes – holding tanks have clearly been the right answer. Hooking up a hose and pulling a lever is FAR more convenient to me that having to lug gallons of yellow liquid around by hand – and find a proper sewer in which to dispose of it, bags of composting material – both before and after use, and having to keep buckets of the “used” stuff around so it can compost for a few months. No thanks.